1. Field
The present disclosure generally relates to a driver circuit for light-emitting diode (LED) bulbs, and, more particularly, to a driver circuit with thermal protection circuitry for preventing damage to an LED bulb that may result from overheating.
2. Description of the Related Art
High temperatures may reduce the operating life of an LED bulb. The LEDs, the driver circuitry, and the cooling system may all be sensitive to heat build-up in the LED bulb. Failure in any one of these components may result in failure of the LED bulb.
The operating temperature of an LED bulb depends on many factors. For example, each individual LED produces heat. Therefore, the number and type of LEDs present in the bulb may affect the amount of heat the LED bulb produces. Additionally, drive circuitry may also produce significant amounts of heat.
Other factors may determine the rate at which generated heat is dissipated. For example, the nature of the enclosure into which the LED bulb is installed may dictate the orientation of the LED bulb, the insulating properties surrounding the LED bulb, and the direction of the convective air stream flowing over the LED bulb. Each of these factors may have a dramatic effect on the build-up of heat in and around the LED bulb.
Accordingly, it may be desirable to dim or turn off the LEDs when the LED bulb or portions of the LED bulb reach certain temperatures. However, the additional circuitry required for this task must fit, along with the other required components, within the limited form factor of the LED bulb.
In the United States, a common lamp bulb form factor is the A19 bulb with the E26 connector, as shown in FIG. 3. LED bulbs must often fit all required components, including the driver circuit, heat sinks, and LEDs, within the A19 bulb and E26 connector. As such, the size and weight of the driver circuit is a significant design consideration because of the limited volume available in the A19 bulb and E26 connector enclosures. LED bulbs meant as replacements for common lamp bulbs in other countries are also limited to comparable volumes.
The limited space in LED bulbs with common bulb form factors prohibits the use of a conventional thermal protection circuit used in microelectronics. This type of circuit usually includes a temperature sensing device, an amplifier, and a switch to turn off the power to the LED bulb. However, the addition of these components to the LED bulb is difficult due to the limited space of common bulb form factors.